US3865607A - Development of image copies provided by differential absorption of liquids - Google Patents

Abstract

An improvement in the method of producing a copy of an original design described in U.S. Pat. No. 3,686,014, in which a layer of liquid formed into a pattern corresponding to the less absorbent areas of the original design is removed from the design-bearing surface of the original on the surface of a roller, from which it is transferred to a copy surface. The improvement comprises developing the liquid pattern by means of a dry developing agent carried by the surface of a roller which has the property of rapidly absorbing surface moisture after wetting by the liquid pattern to bring about the development, and then retaining this moisture, so that by the time the roller has made one revolution, an area of its surface which has been wetted is dry again and ready for re-wetting for further development. The liquid pattern may be developed on the surface of the same roller as that on which it is removed from the design-bearing surface of the original and this roller itself may carry the developing agent or may rotate in contact with a separate roller which carries the developing agent. Alternatively the liquid pattern may be developed after transfer to the copy surface by contact of the latter with the surface of the roller which carries the developing agent. The developing roller may have at least a surface layer which includes a colouring agent for the liquid pattern and this layer may be of porous, permeable or semi-permeable material in respect of the liquid used which is impregnated with, or consists of, or otherwise incorporates the colouring agent.

Description

United States Patent [191 Games 51 Feb. 11, 1975 DEVELOPMENT OF IMAGE COPIES PROVIDED BY DIFFERENTIAL ABSORPTION OF LIQUIDS [75] Inventor: Abram Games, London, England [73] Assignee: Imagic Limited, London, England [22] Filed: Jan. 9, 1973 [21] Appl. No.: 322,179

[30] Foreign Application Priority Data Jan. 11, 1972 Great Britain 1291/72 {52] US. Cl ll7/l.7, 117/13, 117/37 LE, 101/450, 101/468 [51] Int. Cl B44d 5/04, B4lm 5/00 [58] Field of Search ll7/l.7, 37 LE, 13; 101/450, 468, 469

[56] References Cited UNITED STATES PATENTS 3,600,212 8/1971 Labes 101/468 3,686,014 8/1972 Games ll7/l.7

Primary Examiner-Michael Sofocleous Attorney, Agent, or FirmLarson, Taylor & Hinds [57] ABSTRACT An improvement in the method of producing a copy of an original design described in US. Pat. No.

3,686,014, in which a layer of liquid formed into a pattern corresponding to the less absorbent areas of the original design is removed from the design-bearing surface of the original on the surface of a roller, from which it is transferred to a copy surface. The improvement comprises developing the liquid pattern by means of a dry developing agent carried by the surface of a roller which has the property of rapidly absorbing surface moisture after wetting by the liquid pattern to bring about the development, and then retaining this moisture, so that by the time the roller has made one revolution, an area of its surface which has been wetted is dry again and ready for re-wetting for further development.

The liquid pattern may be developed on the surface of the same roller as that on which it is removed from the design-bearing surface of the original and this roller itself may carry the developing agent or may rotate in contact with a separate roller which carries the developing agent. Alternatively the liquid pattern may be developed after transfer to the copy surface by contact of the latter with the surface of the roller which carries the developing agent.

The developing roller may have at least a surface layer which includes a colouring agent for the liquid pattern and this layer may be of porous, permeable or semi-permeable material in respect of the liquid used which is impregnated with, or consists of, or otherwise incorporates the colouring agent.

6 Claims, 4 Drawing Figures DEVELOPMENT OF IMAGE COPIES PROVIDED BY DIFFERENTIAL ABSORPTION OF LIQUIDS This invention relates to the copying of original designs such as typescript, printed or duplicated matter, drawings and other specially prepared original designs, photographs or other representations such as by applied mask and images and patterns of the design, whether on paper or other surfaces and is concerned with a form of process based on the differential absorbency or adsorbency of a range of liquids to differing areas of the design subjected to the liquid, as described in US. Pat. No. 3,686,014.

This specification describes two basic methods of operating the process, in the first of which the original is treated with a liquid from a roller or other supply source and the resulting liquid pattern on image areas is picked up by a second surface, conveniently another roller or sheet. In the second, the liquid is located on a second surface (roller'or sheet) and the liquid pattern is formed on that surface as it is applied to the original. In both methods the liquid pattern may be developed and transferred to a copy surface or alternatively transferred and then developed on the copy surface. The first method usually offers more favourable conditions for the operation of differential absorption and is generally preferred for that reason. The earlier specification describes several methods of development including use of a powder which adheres to the liquid pattern and is then fixed by heat, pressure or solvent; chemical reagents producing a visualised image; pre-treated copysheets producing the reaction with the liquid pattern and also development by dyed sheets. In this last case the liquid pattern dissolves dye on the sheet and leaves a corresponding wet area in the form of a residue which increases progressively as further copies are made with thesame dyed sheet. This residue transfers to new copies unless sufficient time is allowed between copies for drying off or fresh sheets are used each time, adding to expense and inconvenience. The other methods of development also have disadvantages. Somewhat complex mechanical means for delivery and fixing of powder are required if this is to be used cleanly and efficiently; chemical developers as used involve difficulties in storage and deterioration and pre-treated paper also adds to expense and may not always be convenient or available.

Recurrence of a ghost image from the same or successive copies, and resulting from previous contact between the liquid pattern and take-up and/or development members is a further trouble with several of the above methods unless special precautions are taken such as adequately sized rollers, and additional doctor or cleaning members which increase complexity and apparatus size.

According to the present invention a layer of liquid formed into a liquid pattern corresponding to the less absorbent areas of an original design as a result of differential absorption, so that liquid overlies the less absorbent areas, is removed from the design-bearing surface of the original on the surface of a roller, from which it is transferred to a copy surface, the liquid pattern being developed by means of a dry developing agent carried by the surface of a roller which has the property of rapidly absorbing surface moisture after wetting by the liquid pattern to bring about the development, and then retaining this moisture, so that by the time the roller has made one revolution, an area of its surface which has been wetted is dry again and ready for re-wetting for further development either of a subsequent portion of the same liquid pattern or of a dif- 5 ferent liquid pattern. In this way it is possible to overcome the various disadvantages referred to above primarily because the same developing roller can be used over and over again in quick succession without the need to wait for the surface to dry and also without the need for renewing or replenishing the roller.

The terms wet and dry are used to indicate respectively states where an area on the roller is capable of either registering or not an easily discernible image on a second surface. In other words, as long as the roller is capable of producing an image on a second surface, it is regarded as wet, and when no image is produced, the roller is regarded as dry. The fact the surface of the roller is dried by the time it has completed one revolution means that the possibility of ghost images is effectively avoided.

Development of the liquid pattern preferably results from transfer of colouring agent to the pattern from the developing roller. Such colouring agent may take a variety of forms as will be described later. Alternatively, development of the liquid pattern may result from a chemical reaction between the developing agent and the liquid forming the pattern. In order to apply colouring agent, the developing roller needs to have at least a surface layer which includes the colouring agent. This surface layer may be of porous, permeable or semipermeable material in respect of the liquid used and may be impregnated with, consist of, or otherwise incorporate the colouring agent.

The wetted areas on the roller correspond to those of the liquid pattern and contribute sufficient colouration to produce adequate development of the pattern. Consequently immediately after the portion of the surface of the roller has moved away from contact with the liquid pattern which may be on the copysheet, take-up roller or original, it bears a complementary mirror image pattern on its own surface which can itself be transferred to a further surface but due to the characteristic property of at least the surface of the material of the roller in respect of the liquid used, this pattern is progressively absorbed (a term intended to include also adsorbed, imbibed, bonded, retained, or otherwise effectively removed from the surface of the roller by such action) and prevented from being present on the surface in any amount (if at all) or manner likely to interfere with subsequent normal operation. By the time the area in question of the surface of the roller comes into contact with a further liquid pattern the roller surface is sufficiently dry to be in a condition to repeat the sequence just described and produce further develop ments and/or transfers without producing ghost images of previous developments.

The performance of the said materials in concert with appropriate liquids and ingredients leads to commercially valuable advantages by way of substantial reductions in roller diameters and consequent apparatus miniaturisation. Originals of any length may now be copied by the invention using a developing roller for example of only inch diameter and taking under /2 second for a complete revolution and absorption of residual liquid pattern into the surface of the material. There is no loss of efficiency but considerable gains in quality, speed and production costs based on the smaller rollers. In such miniaturised apparatus other rollers such as the take-up roller for the liquid pattern and a possible doctor roller to remove slight residue which might remain on an impervious take-up roller for example may perform with similar advantages in the same manner. It will be understood that since, only a minute amount of liquid exists on roller surfaces for such a short period the process is entirely dry for all practical purposes.

Rate of absorption (hence diameter of roller and apparatus size) can be predetermined by selection of liquid/material/ingredient combinations so that a wide range is provided for operation over normal and specialised applications for industrial use. The invention therefore improves upon and renders more effective the methods of the earlier patent.

The colouring agent may conveniently be in the form of a dye or ink which may be incorporated either in the surface layer or the whole body of the roller. The roller material may be charged with the colouring agent by immersion during or after fabrication to impregnate the material. One method of charging is by the use of dye or ink in a solvent which evaporates to leave the roller coloured but dry. Another method is for finely powdered dyestuffs to be intermixed with the roller material in paste, liquid or powdered form prior to moulding of the roller, the coloured mass after curing or setting resulting in the finished dye-incorporating roller. As a further alternative, the dye powder can be intermixed with a dry powdered form of the material for the roller and the mixture located on a tacky support surface to which it is keyed to form the surface of the roller. Dye powder can also be spread on semi-cured material which retains it after full curing so as to form the surface of the roller.

Rollers prepared in this way can be fabricated as solid cylinders, or outer sleeves may be slipped over cylindrical cores. The use of an outer sleeve is less costly and more economical in materials and provides convenient replacement as the sleeve becomes exhausted through use. Materials can be made up as flat films or sheets and may be wrapped around a central core to form a roller. Sheets can also be made up into endless belts which can be used even in miniature apparatus and permit longer periods for absorption. An endless belt represents a direct mechanical equivalent of a roller and any references both in the body ofthe specification and in the claims to rollers are to be interpreted as including the alternative use of equivalent endless belts.

In a alternative construction of roller in accordance with the invention, the surface of the roller is constituted by a fine-pile fabric charged with powdered developing agent. One particularly appropriate material is fine rayon velvet which can be charged with dye powder by dipping and the excess removed by wiping over. The dye is thus integrated into the pile and will not mark white paper when the material is in contact with.

it. With such a construction, the roller may be hollow to allow the colouring agent to be fed into the pile automatically from the rear side of the fabric, i.e. from within the roller. The gradual feed of dye powder thus ensures a dust-free method. Use of the colouring agent in the form ofa powdered dye can be termed live dye since the dye is not pre-dissolved by contact with solvent and is thus capable of the fullest and most intense response to the liquid pattern. Colouring agent and roller material can be intermixed and sprayed or coated onto a support surface orfthe .two' can .be encapsulated in vesicle form so that the combination produces the desired effect in operation. Y

Chemical reagents may be used in co-operation with the roller as a reinforcement for or instead of dyes, inks and so forth. For example if liquid for the liquid pattern includes ferric chloride the roller may include pyrogallicacid or tannic acid which reacts with the former. Ferric chloride, pyrogallic acid or tannic acid can be intermixed in dry powdered form during initial fabrication of the roller and the liquid pattern then contributes liquid for necessary reaction to produce a coloured image. A starch/iodine reaction can be used. Preparation of the rollers is as before a matter of immersion or im pregnation followed by drying out if needed. As a further form'of developer a minute amount of roller material itself, coloured or not, may be deposited in the manner of a crayon so that the diameter of the roller gradually decreases as it contributes material to the liquid pattern.

Besides developing agents giving visible copies other ingredients intended for industrial applications may be incorporated into the development roller. The specific properties of electro-conductive, etching, resistive, magnetic, insulating-expanding or other ingredients can be exploited in the same manner. Whilst it is normally desirable to incorporate the maximum concentration of developer it is equally important that the ingredient should be fully retained and not leach out or otherwise appear on the surface to which the roller is applied except in liquid pattern areas where these are operative. The finished roller should be surface dry at least and not mark paper or leave powder dust when rolled across. 7

As a general rule the incorporated ingredient should be compatible with the liquid used in order to be activated wholly or partially at least. Various combinations of agents and liquids produce different results but generally speaking aqueous agents should be matched with aqueous liquids and non-aqueous with non-aqueous liquids. The mechanism of extraction of developer may not be by solvent action alone and other factors may be involved. For aqueous liquids strong concentrations of aqueous dyes as used for fibre and felt pens, stamp pad inks, reagents, water colour inks, aqueous pigments and textile dyes are suitable. For non-aqueous liquids, stains and dyes such as Sudan Black and other microscopy dyes, reagents, textile and ceramic dyes and certain printing inks are appropriate and may be of any colour.

For roller materials polyurethane, ethylene-vinyl polymers, ethylene-vinyl acetate, silicone rubbers, PVC as used for surgical plasters, cellulose acetate viscose (Trade Mark cellophane) silk and rayon textiles, cellulosic compounds and membranes, cellulosic cigarette filter rods, demisting films and emulsions as applied to windscreens and goggles, hydrophyllics such as hydromethyl acrylates etc., barata, clay and clay coated materials, zinc oxide coated paper as used for electrostatic copies, highgloss cast coated paper and parchment and parchment papers are examples. In addition to control by matching liquid with material and- /or colourant, further measures can be taken by blending materials to produce the best results. For example, clay or silica powders or Microsieves" (T.M. Union Carbide Ltd) can be intermixed in varying proportions with normally regarded water-impermeable or impervious materials such as silicone rubber pastes or the elastomer Cariflex (T.M. Shell Chemicals Ltd.) or with gums and other colloidal substances so as to produce predetermined degrees of absorbency in the resulting rollers.

The use of rollers constructed in accordance with the invention in any of the ways just described leads to a number of overall advantages when carrying out the method of the earlier patent. These advantages include higher output speeds, higher quality of copies with elimination of possible ghost images, ease of interchangeability by simply exchanging one sleeve or miniature roller for another of a different colour or different developer within the same basic apparatus, cleanliness in handling and operation, lower production costs due to the smaller-sized components and apparatus made possible by the invention and corresponding elimination of complex mechanisms. The sleeves or rollers used are readily disposable or optionally replenished by recharging or by wiping over with a developer which is rapidly integrated into the roller material or by dipping and so forth. Further advantages lie in the ability to copy originals of greater length than the roller circumference owing to the rapid drying of the roller surface, thus making it possible to use miniaturised or other conveniently sized apparatus which can be stored in a desk drawer or is entirely portable in a pocket or briefcase and is accessible for immediate use. Other advantages include the ability to copy very short areas of an original economically by means of the miniature rollers, incorporation of miniaturised apparatus into standard typewriters by clipping on or as an integral part of the unit without adding bulk to the machine.

A method in accordance with the invention is capable of several variations in respect of the point in the process where the developing roller is used. Most simply, the liquid pattern is developed on the surface of the same roller as that on which it is removed from the design-bearing surface of the original. This leads on to two further possibilties. Thus the roller on the surface of which the liquid pattern is removed from the designbearing surface of the original may itself carry the developing agent. Alternatively, this roller may rotate in contact with a second roller which carries the developing agent. A further possibility is for the liquid pattern to be developed after transfer to the copy surface by contact of the latter with the surface of the roller which carries the developing agent.

These various possibilities will now be described in somwhat more detail with reference to the accompanying drawings, in which:

FIG. I is a diagrammatic representation ofa developing roller used in a method in accordance with the invention and illustrating the rapid absorption of the liquid pattern or, in other words, the self-recovery property of the surface of the roller; and

FIGS. 2, 3 and 4 are diagrammatic side views of the different forms of apparatus operating in accordance with the invention.

In FIG. I a developing roller is shown diagrammatically as l and a surface with which it co-operates as 2. As will be explained with reference tothe subsequent Figures, the surface 2 may be the surface of an original to be copied or of a copysheet or, although it is shown as flat for convenience, it may be the surface of another roller. Elements of a liquid pattern are illustrated in grossly exaggerated form as 3. The surface 2 is moving to the left and the roller 1 is rotating in a clockwise direction as indicated by the arrows and, as a result, each element 3 of the pattern comes into contact with the roller 1 in succession. This moistens the developing agent in the surface of the roller 1, thus bringing about development of the elements 3. Developed elements are illustrated as 4, after contact with the roller 1. A proportion of the liquid in the elements 3 remains on the surface of the roller 1 as shown at 5. Owing to the nature of the surface layer of the roller, as previously described in detail, the liquid left on the surface 1 in'the form of elements 5 is rapidly absorbed by any of the physical processes previously described, and the reducing height of successive elements 5 is intended to indicate the successive stages of absorption, successivee elements being shown as 5A, 5B and so forth. By the time the point 5D is reached, the absorption is practically complete and subsequent elements 5E, 5F and so forth are illustrated as having been withdrawn into the interior of the roller. This is purely for purposes of illus tration since in practice the elements will be dispersed by absorption and the depth of penetration will depend entirely on the nature of the surface layer of the roller. It is sufficient to say that when the surface of the roller. 1 leaves the surface 2, it is wet over areas defining the liquid pattern, at some point in its rotation absorption of the liquid is complete and by the time one revolution has been completed the surface of the roller 1 is dry and ready for the development of subsequent elements 3.

This general mechanism of development is followed in the apparatus of each of the succeeding Figures, in each of which the developing roller is shown as shaded both for ease of identification and also to indicate that it contains developing agent which most usually will be black. Each example of apparatus includes a housing shown diagrammatically as 11 and a roller 12 by means of which a layer of liquid is applied to the surface of an original to be copied, shown as 13. The apparatus is to be regarded as moving to the right in relation to the original 13 although, of course, the same effect is obtained if the apparatus is held stationary and the original is moved to the left. In each of the examples there is a second roller in contact with the original 13 and in the interval between the two rollers, the applied layer ofliquid is formed into a pattern by means of the differential absorption previously described. Turning first to the example of FIG. 2, the liquid pattern on the surface of the original 13 is picked up by the developing roller 1 in exactly the same manner as if the original 13 were the surface 2 shown in FIG. 1. The elements of the pattern 5 remaining on the surface of the roller 1 are then transferred to a copysheet 14 as it passes over a roller 15 which thus defines the transfer surface for the developed pattern. The developed pattern on the copysheet 14 is shown as 16 and dries rapidly to form the required copy. The elements of the pattern 5 remaining on the surface of the roller 1 are absorbed as described with reference to FIG. 1 and by the time this roller has made a complete revolution its surface is dry and ready for further contact with the subsequent elements of the liquid pattern.

In the example of FIG. 3 the elements of liquid pattern on the surface of the original 13 are picked up by a roller 20 and one such element is shown as 23. The roller 20 rotates in contact with the developing roller l and each element of the pattern 23 is developed as shown as 24 and is then transferred to the copy surface, again shown as 14 as it passes around a roller 15. Wet areas corresponding to the elements 23 and 24 are left on the roller 1 in the same manner as illustrated in FIG. 1 and are absorbed during the course of rotation so that by the time the surface of the roller 1 again comes into contact with the liquid pattern on the roller 20, it is again completely dry. Although practically all the developed pattern is transferred from the roller to the copy surface 14, there is a risk that a small proportion may be retained, leading to the possibility of a ghost image on the next revolution. For this reason the roller 20 may have properties similar to those of the roller 1, i.e., it may be capable of absorbing any residual developed pattern before further contact with the original 13. Alternatively, a doctor blade or roller (not shown in the drawing) may be fitted in order to clean the roller 20.

FIG. 4 shows a variation of the apparatus of FIG. 3 in which the liquid pattern on the surface of the original 13 is again picked up by a roller 20, but is transferred before development to the copy surface 14 as it passes around the roller 15. One element of the undeveloped pattern is shown at 23 on the roller 20 and elements such as these are transferred to the copy surface 14 and are shortly thereafter developed by the roller 1, the developed elements being shown as 26. As with the previous constructions, wet areas are left on the surface of the developing roller 1 which are absorbed during the course of a revolution so that the roller 1 presents a dry surface to subsequent elements of the liquid pattern on the copy surface 14 as they come into contact with it. As described with reference to FIG. 3, the roller 20 must be so contructed or treated as to have a clean surface before further contact with the original 13.

In each form of the apparatus, therefore, the advantages arising from the characteristics of the developing roller 1 are realised in slightly different ways. In each case, high speed operation is possible with only small diameter rollers.

Examples of copying processes in accordance with the invention and using the different forms of apparatus just described, will now be given.

EXAMPLE 1 This example made use of the apparatus of FIG. 2 and the developing roller 1 is prepared from cold curing RTV 634 Silicone Rubber (T.M. General Electric US.) which was intermixed in its liquid state with a high concentration of Sudan Black dye and poured into a mould of inch diameter. When cured the rubber roller was black throughout and did not mark waste paper. An original was treated with a layer of liquid consisting of UCON (Union Carbide Ltd) and water in equal parts. When the roller traversed the original and then the white copysheet 14 the image areas of the original appeared directly right way round on the copysheet. There was no effective ghost image visible on the copysheet and the roller made upwards of one complete revolution in approximately V2 second.

EXAMPLE 2 The developing roller in Example 1 was used in the apparatus of FIG. 4 in conjunction with a pick-up roller 20 which was identical with the developing roller except for the omission of dye (i.e. having the same absorptive properties) and the same: liquid was used to treat the original. A visible imag'e appeared on a copysheet 14 as the developing roller completeda revolution in contact with the copy surface at a speed of one revolution in approximately A second.

EXAMPLES 3 and 4 Examples 1 and 2 were repeated using methyl salicylate as the liquid for treating the original and similar results were obtained.

EXAMPLE 5 This example made use of the form of apparatus of FIG. 3 and the developing roller 1 was in the form of a A inch diameter rod ofFiltron (a cellulosic cigarette filter material by Cigarette Components Ltd) which was charged by immersion in a solution of Toluene and Sudan Black and allowed to dry so that white paper or an RTV roller wasunmarked when the dyed rod was rolled across. An original was treated with a liquid consisting of Ucon and water in equal parts. The roller 20 was of RTV silicone rubber, of 5 inches circumference which picked up the liquid pattern from the original for development by the roller 1. The liquid pattern on the roller 20 was immediately developed to a blueblack in pattern areas only without repeat or ghost images and was transferred cleanly to the copysheet 14, right way round. The residual image on the surface of the roller 20 was barely visible after transfer but was totally removed bycontact with a film of cellophane or claycoated paper fitted to the apparatus of FIG. 3 so as to engage the roller 20 immediately after its contact with the copy surface 14.

EXAMPLE 6 This example also made use of the apparatus of FIG. 3 including the same construction for the roller 20 as in Example 5. In this case the development roller 1 was in the form of a metal roller of diameter /1 inch having a coating of Demist (Aircraft Instrument Demistors Ltd.) which was charged with water soluble black dye from a Pentel fibre tipped pen. If set for 2 minutes the black dye is dry and does not mark white paper. The original to be copied was treated with liquid consisting of diethylene glycol and water in equal parts. The liquid pattern on the roller 20 was developed by the roller 1 and transferred to the copy surface as a black, right way round image.

EXAMPLE 7 This example made use of the apparatus of FIG. 2 in which the developing roller 1 was formed by charging a sheet of Cellophane (T.M.) with Pentel water soluble dye and allowing it to dry so that paper was unmarked by contact with it. The sheet was attached to a inch diameter roller surface to form a roller covering. The original to be copied was treated with liquid consisting of diethylene glycol and water in equal parts. Engagement of the roller 1 with the copy surface 14 produced a visible image without the appearance of any ghost images as the roller made more than one complete revolution.

EXAMPLE 8 This example made use of the apparatus of FIG. 4 and the developing roller 1 was prepared by charging rayon velvet of high intensity pile with water-soluble Dylon dye (Dylon Ltd) in finely powdered form by dipping in the powder and excess removed by vibration and wiping over. The velvet left no mark when contacted with white paper and was wrapped around a core to form a roller of 43 inch diameter. The original to be copied was treated with liquid consisting of diethylene glycol and water in equal parts to form a liquid pattern which was transferred by the roller to the copy surface 14 where it was developed by the roller just described. The image was coloured in the same colour as the dye used, non-image areas remaining clear of colour and without ghost images after more than one revolution of the developing roller.

EXAMPLE 9 This example was the same as Example 8 except that in preparing the developing roller, the velvet was charged by immersion in stamp pad ink and then dried. Apart from the colour, the results obtained were the same as for Example 8.

in both the last two examples, no free solid colouring agent was visible at the surface of the pile, but the effect of the liquid in the pattern was to extract colour from the body of the pile so as to achieve effective development.

I claim:

1. In a method of producing a copy of an original design carried by a surface which is such that the absorbency to a range of liquids differs either between the image and non-image areas or between contiguous image areas, or both, which comprises the steps of providing a layer of liquid from said range on said surface to form a liquid pattern on said surface corresponding to the less absorbent areas of the original design as a result of the differential absorption, contacting the liquid pattern on said surface with a transfer roller to transfer liquid in said pattern from said surface to the transfer roller surface, transferring the liquid pattern from said transfer roller surface to a copy surface, and developing said liquid pattern, the improvement wherein said step of developing comprises contacting said liquid pattern with a dry developing agent carried by the surface of a developer roller which has the property of rapidly absorbing surface moisture after wetting by the liquid pattern to bring about the development, and then retaining this liquid, so that by the time the developer roller has made one revolution, an area of its surface which has been wetted with the liquid of said liquid pattern is dry again and ready for being re-wetted for further development either of a subsequent portion of the same liquid pattern or of a different liquid pattern.

2. A method according to claim 1, in which the step of developing comprise developing said liquid pattern on said transfer roller surface.

3. A method according to claim 2, in which said transfer roller is the roller which carries the developing agent.

4. A method according to claim 2, in which said transfer roller rotates in contact with said developer roller.

-5. A method according to claim 1, in which the step of developing comprises developing said liquid pattern on said copy surface.

6. A method according to claim 1 in which said dry developing agent comprises coloring agent and in which development of the liquid pattern results from transfer, from the developing roller, of coloring agent to the liquid pattern.

Claims (6)

1. IN A METHOD OF PRODUCING A COPY OF AN ORIGINAL DESIGN CARRIED BY A SURFACE WHICH IS SUCH THAT THE ABSORBENCY TO A RANGE OF LIQUIDS DIFFERS EITHER BETWEEN THE IMAGE AREAS, OR BOTH, IMAGE AREAS OF BETWEEN CONTIGUOUS IMAGE AREAS, OR BOTH WHICH COMPRISES THE STEPS OF PROVIDING A LAYER OF LIQUID FROM SAID RANGE ON SAID SURFACE TO FORM A LIQUID PATTERN ON SAID SURFACE CORRESPONDING TO THE LESS ABSORBENT AREAS OF THE ORIGINAL DESIGN AS A RESULT OF THE DIFFERENTIAL ABSORPTION, CONTACTING THE LIQUID PATTERN ON SAID SURFACE WITH A TRANSFER ROLLER TO TRANSFER LIQUID IN SAID PATTERN FROM SAID SURFACE TO THE TRANSFER ROLLER SURFACE, TRANSFERRING THE LIQUID PATTERN FROM SAID TRANSFER ROLLER SURFACE TO A COPY SURFACE, AND DEVELOPING SAID LIQUID PATTERN, THE IMPROVEMENT WHEREIN SAID STEP OF DEVELOPING COMPRISES CONTACTING SAID LIQUID PATTERN WITH A DRY DEVELOPING AGENT CARRIED BY THE SURFACE OF A DEVELOPER ROLLER WHICH HAS THE PROPERTY OF RAPIDLY ABSORBING SURFACE MOISTURE AFTER WET-

2. A method according to claim 1, in which the step of developing comprise developing said liquid pattern on said transfer roller surface.

3. A method according to claim 2, in which said transfer roller is the roller which carries the developing agent.

4. A method according to claim 2, in which said transfer roller rotates in contact with said developer roller.

5. A method according to claim 1, in which the step of developing comprises developing said liquid pattern on said copy surface.

6. A method according to claim 1 in which said dry developing agent comprises coloring agent and in which development of the liquid pattern results from transfer, from the developing roller, of coloring agent to the liquid pattern.

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